It's been a few years since I've installed ETO, so I wanted to make sure I got it right. I notice that ground facility flags are spawning random nations, even ones outside of the time period of the era I select. I can't remember if that's always been a thing that's happened. Is there something I messed up or just how the game handles loading them in?
I'm glad someone else has noticed this in ETO. I posted some screenies about it years ago (getting NZ flags on the allied side of the frontline, and SCW flags on the Axis side) - wierd stuff like that! I even added #flags to some facilities (eg invasion defences) so I could get a clearer idea of what's going on.
One of the problems with random nationalities is that for some facilities specifying a lot of vehicles, the randomly assigned nation does not have a vehicle for every type - hence you get facilities which are pretty empty and missing spawned components.
My first guess was that my experiments with the country.xml file, where I change the default spawning nations for air spawns and vehicle spawns, also allowed the random nationalities for facility spawns. But maybe it has always been there and no-one has mentioned it?
IIRC in one of the SDKs, it is mentioned that facilites DO spawn with random nationalities for the relevant alliance (I just never believed it was commonplace). It will likely either be the mission and spawn scripting SDK or the Campaign SDK which mentions it.
I consider it both a blessing and a curse that I notice these small things because now I find myself searching for the flags during strafe runs. I actually came across your post a little bit after posting as I was curious to search if someone else had noticed. It is pretty strange indeed. Maybe it's an inherent game mechanic we may not have a choice in changing, but I hope to be wrong about that.